By AOMEI / Last Updated October 14, 2019

Why extend C drive in Windows 10?

After using computer with Windows 10 installed for a long time, you may encounter Low Disk Space warning on C drive. It is really a troublesome issue especially for the user whose work depends on computer such as game testers, editors, designers. To fix it, you may want to extend C drive.

Three ways to extend system partition

Usually, your C drive is the drive that contains OS partition. Here offers you three effective and simple ways about how to increase C drive space. You can choose one according to your demand.

Way 1. Extend C drive when there is no contiguous unallocated space

In many cases, you couldn’t find an adjacent unallocated space behind the system partition. At this time, you’ll find that Extend Volume greyed out if you right click C drive.

And you’d better employ third-party partition manager software, such as AOMEI Partition Assistant Professional. The feature Extend Partition Wizard in it allows you to extend system C drive in Windows 10 within few clicks even when a contiguous unallocated space doesn’t exist. Install it and have a look at how it works.

To learn how to extend system partition in Windows 10, you should pay attention to the following things and then you can start learning.

▶Make sure there is free space in the partition which plan to add into system partition.

▶Make sure all the running applications in the partition that you are going to operate have been closed.

▶Don’t cut off power until the task has finished.

Step 1. Run AOMEI Partition Assistant Professional. Click Extend Partition Wizard on the left side of the interface.

All Tools

Step 2. In the pop-up window, there are two choices. To expand system click Extend system partition and then click Next.

Extend Partition Method

Step 3. Click the partition which you want to add free space from then click Next to continue.

Select Partitions

Step 4. Right move the bar to decide the size of free space you need add into c Drive. Then click Next.

Extend Size

Step 5. Click Proceed to operate the task then you can extend C drive.



  • If there is unallocated space on the hard drive, you can use Merge Partition feature to add the unallocated space directly to system partition or merge partitions in Windows 10 without data loss.

  • AOMEI Partition Assistant Professional is a version for home users; if you are a Server users, AOMEI Partition Assistant Server is suitable for you.

Way 2. Extend C drive via Disk Management with adjacent unallocated space

If there is an adjacent unallocated space behind C drive, you can extend it in Windows 10 Disk Management.

Here are detailed steps:

Step 1. Press Windows + R at the same time to open Run dialogue.

Step 2. Input diskmgmt.msc and hit Enter to open Disk Management.

Step 3. Right click C drive and choose Extend Volume.

Step 4. Follow the prompts that will appear to complete this operation.

Way 2. Increase C drive via Diskaprt with contiguous unallocated space

When there is a contiguous adjacent unallocated space behind system partition, you can also choose to extend it in Diskpart utility.

Step 1. Open Run dialogue, input diskpart and click OK.

Step 2. Run commands as follows:

  • list disk

  • select disk n

  • list partition

  • select partition m

  • extend size= x


  • n refers to the number of the disk that holds C drive.

  • m is the number of C drive.

  • x is the size in MB you want to add to the system partition.

Final words

Obviously, it’s not hard to extend C drive in Windows 10 even there is no contiguous unallocated space behind it. Among the three listed solutions, choose one based on the specific situation. Apart from increasing system drive in Windows 10, these ways also can be applied in Windows 7/8/8.1.